JPH116755A - Interface detection switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an interface detection switch with high precision by a method wherein a detection value of both first and second sensors is differentialcalculated to detect an interface. SOLUTION: An interface detection circuit 25 differential-calculates a detection value of a first sensor 21 and a detection value of a second sensor 23 and detects an interface 8. In this case, the first sensor 21 and the second sensor 23 make use of difference in a dielectric constant and a conductivity of liquid, and measures electrostatic capacity (a dielectric constant) or a resistance value (a conductivity). These values are compared with a set threshold level, so that detection of the interface is made. Thus, as the sensor parts 21, 23 are made as a differential structure, it is possible to obtain an interface detection switch with excellent precision which is not affected if the sensor parts 21, 23 are stained by adhesion of an oil film, etc., and a dielectric constant (a conductivity) to be measured is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interface detection switch having a simple structure and improved accuracy. More specifically, the present invention relates to an interface detection switch in which a sensor portion has a differential configuration to cancel an error caused by substances contained in two liquids.

[0002]

2. Description of the Related Art FIG. 5 is an explanatory view of the structure of a conventional example generally used in the prior art. For example, catalog name; general catalog "NOHKEN", page 54, page 63, page 104, date of issue; May 5, Issued by Norken Co., Ltd. Here, an example used for detecting a waste liquid in which water and oil are mixed will be described.

In FIG. 1, reference numeral 1 denotes an oil / water separation tank. The oil / water separation tank 1 separates the waste liquid of oil 2 and water 3 for a predetermined period of time to separate the oil 2 and water 3 due to the difference in specific gravity. 5 is an injection pipe for injecting the mixed waste liquid 6 of the oil 2 and the water 3 into the oil-water separation tank 1.

[0004] Reference numeral 7 denotes a capacitance type (electric resistance type) level sensor which is used as an interface detection switch for detecting an interface between the oil 2 and the water 3. In this case, the interface detection switch 7 utilizes the difference in the dielectric constant and conductivity of the liquid, and is installed at a predetermined height in the oil / water separation tank 1.
At this position, the capacitance (dielectric constant) or the resistance value (conductivity) is measured. The interface is detected by comparing these values with the set threshold level.

[0005] Reference numeral 8 denotes an interface detection position. 9 is an oil discharge valve provided in the oil / water separation tank 1 at a position above the interface detection switch 7. The waste oil 11 is discharged from the oil discharge valve 9.

Reference numeral 12 denotes a water discharge valve provided in the oil / water separation tank 1 at a position below the interface detection switch 7. Waste water 13 is discharged from the water discharge valve 12. hw is the height of the waste water outlet,
hs indicates switch installation height = desired detection level, and ho indicates waste oil port height.

In the above configuration, the following operation steps are performed. (A) The mixed waste liquid 6 of the oil 2 and the water 3 is taken into the oil / water separation tank 1 from the injection pipe 5. (B) When a certain amount is taken in, the taking-in of the mixed waste liquid 6 from the injection pipe 5 to the oil / water separation tank 1 is stopped.

(C) Leave for a predetermined time. The standing time is determined in consideration of, for example, the degree to which the waste liquid 6 is stirred. (D) When the interface detection switch 7 detects the oil 2,
The oil discharge valve 9 is opened, and the waste oil is discharged. Next, step (h)
Move on to

(E) When the interface detection switch 7 detects the water 3, the water discharge valve 12 is opened and the waste water 13 is discharged. (F) When the interface detection switch 7 detects the oil layer 2, the water discharge valve 12 is closed.

(G) The oil discharge valve 9 is opened to discharge the oil 2 floating on the water surface of the oil / water separation tank 1. (H) After a predetermined time, the oil discharge valve 9 is closed. Thereafter, the steps (a) to (h) are repeated. As described above, the oil 2 and the water 3 in the waste liquid are separated and discharged.

[0011]

However, in such an apparatus, (1) when an oil film or the like adheres to the interface detection switch 7,
Since the dielectric constant (conductivity) changes, it causes an error. (2) A complicated circuit method such as synchronous detection is required for a measurement circuit for measuring capacitance or the like.

The present invention solves this problem. An object of the present invention is to provide an interface detection switch having a simple configuration and improved accuracy.

[0013]

In order to achieve this object, the present invention provides: (1) an interface detection for detecting an interface between two separated liquids by using a corresponding pair of electrodes as a sensor; A first sensor disposed at a predetermined position of a separation tank having a bottom filled with the two liquids, and a second sensor disposed at a predetermined position on the bottom side of the first sensor of the separation tank. 2. An interface detection switch, comprising: two sensors; and an interface detection circuit that detects the interface by performing a differential operation on a detection value of the first sensor and a detection value of the second sensor. (2) The first and second sensors are sensors for detecting the absolute value of the impedance of the two liquids in which the magnitude relationship of the permittivity and the magnitude relationship of the conductivity of the two fluids have the same relationship. The interface detection switch according to claim 1, wherein (3) The first and second sensors include a printed board, and one electrode of the first sensor, the other electrode of the first sensor, and 3. The interface detection switch according to claim 1, wherein one of the electrodes of the second sensor and the other of the second sensor are arranged. It is what constituted.

[0014]

In the above configuration, the following operation steps are performed. (A) The mixed waste liquid of oil and water is taken into the oil / water separation tank from the injection pipe. (B) When a certain amount is taken in, stop taking in the mixed waste liquid from the injection pipe to the oil / water separation tank.

(C) Leave for a predetermined time. The standing time is determined in consideration of the degree to which the waste liquid is agitated. (D) When the interface detection switch detects oil, the oil discharge valve is opened and waste oil is discharged. Next, the process proceeds to step (h).

(E) When the interface detection switch detects water, the water discharge valve is opened to discharge waste water. (F) When the interface detection switch detects the oil layer, the water discharge valve is closed.

(G) Open the oil discharge valve and discharge the oil floating on the water surface of the oil / water separation tank. (H) After a predetermined time, the oil discharge valve is closed. Thereafter, the steps (a) to (h) are repeated. As described above, the oil and water in the waste liquid are separated and discharged. Hereinafter, a detailed description will be given based on embodiments.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram illustrating the principle of an embodiment of the present invention. In the figure, the configuration of the same symbol as FIG. 5 represents the same function. Hereinafter, only differences from FIG. 5 will be described.

Reference numeral 21 denotes a bottom portion 2 filled with two liquids 2 and 3.
Of the oil-water separation tank 1 having
Sensor. In this case, the pair of electrodes 211 and 21
2.

Reference numeral 23 denotes the first sensor 2 of the oil / water separation tank 1.
The second sensor is located at a predetermined position on the bottom portion 22 side of the first sensor. In this case, it is constituted by a pair of electrodes 231 and 232.

The first sensor 21 and the second sensor 23 are arranged such that an intermediate point between the first sensor 21 and the second sensor 23 is a predetermined interface detection position 8.

Reference numeral 24 denotes a drive circuit for driving the first sensor 21 and the second sensor 23. In this case, it is driven by a sine wave. 25 is a detection value of the first sensor 21;
This is an interface detection circuit that detects the interface 8 by performing a differential operation on the detection value of the second sensor 23.

In this case, the first sensor 21 and the second sensor 23 make use of the difference in the dielectric constant and the electric conductivity of the liquid, and the capacitance (dielectric constant) or the resistance value (the electric conductivity) ) Is measured. The interface is detected by comparing these values with the set threshold level.

In the above configuration, the following operation steps are performed. (A) The mixed waste liquid 6 of the oil 2 and the water 3 is taken into the oil / water separation tank 1 from the injection pipe 5. (B) When a certain amount is taken in, the taking-in of the mixed waste liquid 6 from the injection pipe 5 to the oil / water separation tank 1 is stopped.

(C) Leave for a predetermined time. The standing time is determined in consideration of, for example, the degree to which the waste liquid 6 is stirred. (D) When the interface detection switch 7 detects the oil 2,
The oil discharge valve 9 is opened, and the waste oil is discharged. Next, step (h)
Move on to

(E) When the interface detection switch 7 detects the water 3, the water discharge valve 12 is opened and the waste water 13 is discharged. (F) When the interface detection switch 7 detects the oil layer 2, the water discharge valve 12 is closed.

(G) The oil discharge valve 9 is opened to discharge the oil 2 floating on the water surface of the oil / water separation tank 1. (H) After a predetermined time, the oil discharge valve 9 is closed. Thereafter, the steps (a) to (h) are repeated. As described above, the oil 2 and the water 3 in the waste liquid are separated and discharged.

As a result, since the sensor portions 21 and 23 are of a differential configuration, even if the sensor portions 21 and 23 become dirty due to adhesion of an oil film or the like and the measured dielectric constant (conductivity) changes, the influence is not affected. An interface detection switch with good accuracy can be obtained without receiving the same.

FIG. 2 is an explanatory view of a main part configuration of another embodiment of the present invention. In the present embodiment, 31 is the two liquids 2,
3 is a first sensor arranged at a predetermined position in the oil-water separation tank 1 having a bottom 22 and filled with the same. In this case, it is constituted by a pair of electrodes 311 and 312.

Reference numeral 33 denotes the first sensor 3 of the oil / water separation tank 1.
The second sensor is located at a predetermined position on the bottom portion 22 side of the first sensor. In this case, it is constituted by a pair of electrodes 331 and 332.

The first sensor 31 and the second sensor 33 are arranged such that an intermediate point between the first sensor 31 and the second sensor 33 is a predetermined interface detection position 8.

Reference numeral 34 denotes a drive circuit for driving the first sensor 31 and the second sensor 33. In this case, it is driven by a sine wave. 35 is a detection value of the first sensor 31;
This is an interface detection circuit that performs a differential operation on the detection value of the second sensor 33 and detects the interface 8.

In this case, the first sensor 31 and the second sensor 33 measure the absolute value of the impedance of the liquid. Therefore, in the interface detection circuit 35, the first sensor 31
The difference between the absolute value of the impedance of the second sensor 33 and that of the second sensor 33 is measured.

FIG. 3 shows the difference in electrical characteristics between water and oil. In FIG. 3, the capacitance, the resistance value, and the impedance value are values obtained by a pair of electrodes having a spacing of 1 cm and a size of 1 cm square, and the frequency of the impedance value is 1 MHz.

Water and oil have the same relationship between the dielectric constant and the electrical conductivity. (Both quantities are larger in the case of water.) Therefore, it can be seen that the absolute value of the impedance, which is their total quantity, may be compared.

Since the absolute value of the impedance is an amount corresponding to the reciprocal of the permittivity or the conductivity, the magnitude of water is smaller in the magnitude relation. In the conventional interface detection switch 7 shown in FIG. 5, for example, the electrodes are driven by a sine wave voltage by a drive circuit, the current flowing through the electrodes is measured, and the permittivity (capacitance) and the conductivity (conductivity) are determined by the circuit. I was doing calculations. However, in these measurements, the obtained current must be performed by a complicated method such as synchronous detection.

On the other hand, the measurement of the absolute value of the impedance only requires obtaining the absolute value of the obtained current, so that the configuration of the measuring circuit can be very simplified. Therefore, an inexpensive interface detection switch can be obtained.

As shown in FIG. 1, the first and second sensors 21 and 23 are provided above and below the interface detection position 8 and differential detection is performed, so that even when an oil film or the like adheres to the electrode surface. , The effect is small.

In the conventional detection with one sensor,
Due to the adhesion of the oil film or the like, the capacitance and the resistance value change, and an error may occur depending on a preset threshold level.

Since it is considered that the oil film adheres to the electrode surface on average, the influence of the adhesion can be reduced by using the two sensors 21 and 23 differentially as in this embodiment. In the above-described embodiment, oil-water separation has been described. However, the present invention is not limited to this, and can be used for detecting the interface between two liquids in which the magnitude relationship of the dielectric constant and the magnitude relationship of the conductivity are the same.

FIG. 4 is an explanatory diagram of a main part configuration of another embodiment of the present invention. In this embodiment, one electrode 421 of the first sensor 42, the other electrode 422 of the first sensor 42, and the second electrode 421 are sequentially arranged on one surface of the printed circuit board 41 in the direction of the bottom 22 of the oil-water separation tank 1. One electrode 43 of the sensor 43
First and second electrodes 43 of the sensor 43 are arranged.

Reference numerals 44 and 45 are connectors provided on the printed circuit board 41. Reference numeral 46 denotes a lead for connecting the connector 44 and one electrode 421 of the first sensor 42. 47 is a lead connecting the connector 44 and the other electrode 422 of the first sensor 42.

48 denotes a connector 45 and the second sensor 43
Are connected to one of the electrodes 431. 49
Is the connector 45 and the other electrode 43 of the second sensor 43.
2 is a lead connecting to

As a result, as shown in FIG. 4, the detection portion is formed of a single printed circuit board 41, so that an ordinary manufacturing apparatus can be used, so that an inexpensive interface detection switch can be obtained.

[0045]

As described in detail above, according to the first aspect of the present invention, since the sensor portion has a differential configuration, the sensor portion is contaminated due to adhesion of an oil film or the like, and the measured dielectric constant ( Even if the (conductivity) changes, an accurate interface detection switch can be obtained without being affected.

According to the second aspect of the present invention, the absolute value measurement of the impedance can be adopted under a certain condition. Therefore, the absolute value measurement of the impedance only requires the absolute value of the obtained current. The configuration is very simple. Therefore, an inexpensive interface detection switch can be obtained.

According to the third aspect of the present invention, since the detecting portion is constituted by a single printed circuit board, an ordinary manufacturing apparatus can be used, so that an inexpensive interface detecting switch can be obtained.

Therefore, according to the present invention, an interface detection switch having a simple configuration and improved accuracy can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of FIG. 2;

FIG. 4 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 5 is an explanatory diagram of a configuration of a conventional example generally used in the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oil-water separation tank 2 Oil 3 Water 4 Emulsion 5 Injection pipe 6 Mixed waste liquid 7 Interface detection switch 8 Interface detection position 9 Oil discharge valve 11 Waste oil 12 Water discharge valve 13 Waste water 21 First sensor 211 Electrode 212 Electrode 22 Bottom 23 Second Sensor 231 electrode 232 electrode 24 drive circuit 25 interface detection circuit 31 first sensor 311 electrode 312 electrode 33 second sensor 331 electrode 332 electrode 34 drive circuit 35 interface detection circuit 41 printed circuit board 42 first sensor 421 electrode 422 electrode 43 second sensor 431 electrode 432 electrode 44 connector 45 connector 46 lead 47 lead 48 lead 49 lead hw wastewater port height hs sensor installation height = desired detection level ho waste oil port height

Claims (3)

[Claims] 1. An interface detection switch for detecting an interface between two separated liquids using a pair of corresponding electrodes as a sensor, wherein a predetermined position of a separation tank filled with the two liquids and having a bottom. A second sensor disposed at a predetermined position on the bottom side of the first sensor in the separation tank; a detection value of the first sensor and the second sensor And an interface detecting circuit for detecting the interface by performing a differential operation on the detected value of the interface. 2. The first and second sensors detect the absolute value of the impedance of the two liquids in which the magnitude relationship of the permittivity and the magnitude relationship of the conductivity of the two fluids have the same relationship. 2. The interface detection switch according to claim 1, wherein the sensor is a sensor that performs detection. 3. The first and second sensors include: a printed circuit board; one electrode of the first sensor, the other electrode of the first sensor sequentially arranged on one surface of the printed circuit board in the direction of the bottom;
3. The interface detection switch according to claim 1, wherein one of the electrodes of the second sensor and the other of the second sensor are arranged.